Simplify the expression. $(-2r^{4})(-r^{3}-2r^{2}-7r)$
Explanation: First use the distributive property. $ - 2 r^4 (- r^3) - 2 r^4 (-2 r^2) - 2 r^4 (-7 r) $ Simplify. $2r^{7}+4r^{6}+14r^{5}$